http://www.vb1000.com/ makes digital ballast and I think a few others do too.

Yes the owner of advanced nutrients is working with another company in Canada to make one ballast that would run 4 HPS lights. But thatâ??s nothing new there are warehouses running 3-phase transformers running 50 lights at a time. My area if engineering is more communication and broadband but I know whom to call. Pacific Transformers makes custom application transformers still I believe. It may be worth a phone call. I would think digital versions are many years away.